The present invention relates to a gas-liquid mixture especially for use as a fire extinguishing agent, a fire extinguishing unit comprising the gas-liquid mixture, and a method for using the gas-liquid mixture.
Fire extinguishing agents are consumed in large amounts all over the world for fire protection in airplanes, ships, computer rooms, laboratories etc. Fire extinguishing agents are used both at home and in industry. A large consumer, of course in addition to fire departments, is the armed forces which also use large quantities for training purposes.
A standard agent for extinguishing fire is water, but in many cases water does greater damage than the fire itself, and besides water is unsuitable for extinguishing fire in e.g. electrical appliances. Carbon dioxide is also a fire extinguishing agent that is frequently used, but nor can this be used for all types of fire.
The searching for a clean, effective, non-toxic and also inexpensive fire extinguishing agent was initiated at the beginning of the 20th century. Then the so-called halons were developed. Halon is a tradename and comprises a number of halogenated hydrocarbons. The halon compounds are different combinations of carbon, chlorine, fluorine and bromine.
Two types of halon gas have been predominant, Halon 1301 and Halon 1211. Halon 1301 has mainly been used in so-called total flooding systems, and Halon 1211 has been used for hand-held extinguishers and so-called mobile fire extinguishing units (wheel-mounted or in fire-engines). Halon 1211 has also been used in permanent installations, such as local application systems. A further important field of application for Halon 1211 is the protection of different types of vehicle, civilian as well as military. Generally, engine compartments and other machinery spaces are to be protected, but also personnel rooms are objects to be protected.
The reason why several types of halon gas have been used is, among other things, their physical properties in relation to their field of application. Here, the boiling point, steam pressure and toxicity have been predominant parameters.
These halons are clean, effective and relatively non-toxic fire extinguishing agents, but in the 1970's it was considered to be proved that the halons had a strongly ozone-depleting effect. Since then a large number of the countries in the world have decided and bound themselves to reduce and, in the long run, discontinue the production and use of halons. The world production of fire extinguishing agents and particularly the halons is enormous. Merely in respect of Halon 1211 which in the first place is an agent for small and medium size portable fire extinguishers, the 1986 production amounted to 20,000 tons. There is thus an increasing interest all over the world to find a replacement for the halons.
A large number of experiments of finding such a replacement have already been made, but so far none has appeared to be as effective as halons and at the same time harmless to the environment.
Today it is required that a satisfactory fire extinguishing agent should be effective, non-toxic and harmless to the environment. The environmental aspect is today of utmost importance, and a new fire extinguishing agent should have above all a low ozone-depleting effect and a low greenhouse effect. The ozone-depleting effect is stated as an ODP value (Ozone Depletion Potential), and the greenhouse effect is stated as a GWP value (Global Warming Potential). The calculation of these values is well known within the art and will here not be discussed in more detail. The standard values of different countries have not been stipulated, but it is obvious that they will be substantially lower than the values of today's commercial halogen gases.
It is further required that a new fire extinguishing agent should be possible to use to refill existing containers ("drop-in agent"), without necessitating any large and expensive operations. Above all this applies to hand-held fire extinguishers since they are available in enormous amounts. Replacement of a nozzle or gasket could perhaps be accepted, but it would be far too expensive if for example the entire valve system had to be replaced.
One of the problems of finding a replacement for the halons is that, unfortunately, many agents which are less harmless to the environment and at the same time non-toxic are also less effective. For example, brominated hydrocarbons are effective but, on the other hand, highly toxic.
The aim of some experiments of finding a replacement has been to change from fully halogenated into semi-halogenated hydrocarbons, thereby especially reducing the amount of chlorine. Experiments with fully fluorinated hydrocarbons have also been performed. However, the agents become less effective when you pass from bromine to chlorine and then to fluorine. In respect of toxicity the opposite applies, i.e. bromine is the most toxic one and fluorine the least toxic, at least in combination with carbon.
The aim of other experiments has been to try to render a per se less effective agent more effective by means of different types of nozzles. For instance, there has been a great deal of work with the spreading of the agent precisely in the nozzle and pressure variations in the nozzle. The new agents which are less harmless to the environment are mainly liquids, and it has been tried in different ways to give these agents the energy required to obtain a sufficient streaming effect. There have also been experiments of adding various clean gases.
None of the experiments which are known so far has, however, resulted in a fire extinguishing agent that could replace today's halon gases.
One of the grounds for the present invention is the inventor's assumption that for replacing the above-mentioned, predominant types of halon gas, while also taking the new environmental parameters the ODP and GWP factors into consideration, it is not possible to design one or two "replacement gases" which satisfy both the old and the newly added requirements.
For a perfectly satisfactory and acceptable solution of the problem in future it is the inventor's opinion that it is not possible to design in a chemico-technical manner two gases with the qualities of Halon 1301 and 1211, but without unacceptable environmental or toxic side-effects.
The solution is the finding of a formula or a method for developing a replacement gas for different fields of application while considering the specific parameters that apply to the application involved. To achieve this, the replacement gases must in future be custom-made for their purpose. A much larger number of variants will be necessary to meet all the applications which are of interest for this type of fire extinguishing agent (so-called clean fire extinguishing agents).